Universal Ruler
To measure a segment using a ruler, you need to align the ruler so that one end of the segment matches a mark on the ruler, and the other end matches another mark. The segment's length is then the difference between the numbers at these two marks.
You have a plain ruler of sufficient length without any marks. Your task is to place the fewest possible marks on this ruler so that you can measure any integer segment length from l to r.
Input
The first line of the input contains two integers l and r (1 ≤ l ≤ r ≤ 23).
Output
On the first line of the output, print the minimum number of marks needed to measure all segment lengths from l to r. On the second line, list the required marks in ascending order. All numbers must be integers and should not exceed 10000 in absolute value.